Apparatus and method for determining an approximation of the stroke volume and the cardiac output of the heart
First Claim
1. An apparatus for determining an approximate value for a stroke volume SV (in milliliter) of a subject'"'"'s heart, comprisinga) means for measuring an electrical impedance Z(t) of a part of the subject'"'"'s body, wherein a value of said electrical impedance Z(t) changes with time t as a consequence of the beating of the heart;
- b) means for determining a base impedance Z0 as a part of said electrical impedance Z(t) which does not change significantly during a period of one cardiac cycle;
c) means for determining a peak magnitude
of a temporal derivative
of said electrical impedance Z(t), indicating an absolute maximum rate of change of said electrical impedance Z(t) during a systolic period of the cardiac cycle;
d) means for determining a left ventricular ejection time, TLVE;
e) means for determining the cardiac cycle period TRR of the heart; and
f) means for calculating said approximate value of the stroke volume SV wherein said calculating means is adapted to evaluate a formula wherein 0.15≦
n≦
0.8 and 0≦
m≦
1.5,and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant.
1 Assignment
0 Petitions
Accused Products
Abstract
The invention relates to an apparatus and a method for determining an approximate value for the stroke volume and the cardiac output of a person'"'"'s heart. The apparatus and method employ a measured electrical impedance, or admittance, of a part of a person'"'"'s body, namely, the thorax. This part of a person'"'"'s body is chosen because its electrical impedance, or admittance, changes with time as a consequence of the periodic beating of the heart. Accordingly, the measured electrical admittance or impedance can provide information about the performance of the heart as a pump.
-
Citations
140 Claims
-
1. An apparatus for determining an approximate value for a stroke volume SV (in milliliter) of a subject'"'"'s heart, comprising
a) means for measuring an electrical impedance Z(t) of a part of the subject'"'"'s body, wherein a value of said electrical impedance Z(t) changes with time t as a consequence of the beating of the heart; -
b) means for determining a base impedance Z0 as a part of said electrical impedance Z(t) which does not change significantly during a period of one cardiac cycle;
c) means for determining a peak magnitude
of a temporal derivative
of said electrical impedance Z(t), indicating an absolute maximum rate of change of said electrical impedance Z(t) during a systolic period of the cardiac cycle;
d) means for determining a left ventricular ejection time, TLVE;
e) means for determining the cardiac cycle period TRR of the heart; and
f) means for calculating said approximate value of the stroke volume SV wherein said calculating means is adapted to evaluate a formula wherein 0.15≦
n≦
0.8 and 0≦
m≦
1.5,and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
(in milliliter), wherein W is the subject'"'"'s weight in kilogram (kg), wherein C3 is a coefficient with constant value and X and N are exponents with constant values, wherein mZ{overscore (T)}=1 for Z0≧
ZC, andfor Z0<
ZC, and wherein ZC is a constant, and wherein C2 is a constant.
-
-
9. The apparatus of claim 8, wherein C2=0.
-
10. The apparatus of claim 8, wherein C3 is a value in the range of 0.01-15.
-
11. The apparatus of claim 10, wherein C3 is approximately 13.
-
12. The apparatus of claim 8, wherein X is a value in the range of 0.9-1.1.
-
13. The apparatus of claim 12, wherein X is approximately 1.025.
-
14. The apparatus of claim 8, wherein N is a value in the range of 1.0-2.0.
-
15. The apparatus of claim 14, wherein N is approximately 1.5.
-
16. The apparatus of claim 8, wherein Zc is a value in the range of 15-25Ω
- .
-
17. The apparatus of claim 16, wherein ZC is approximately 20Ω
- .
-
18. The apparatus of claim 1, wherein VEFF=C3·
- WX (in milliliter), wherein W is the subject'"'"'s weight in kilogram, and wherein C3 is a coefficient with a constant value and X is an exponent with constant value.
-
19. The apparatus of claim 18, wherein C3 is a value in the range of 0.01-15.
-
20. The apparatus of claim 19, wherein C3 is approximately 13.
-
21. The apparatus of claim 18, wherein X is a value in the range of 0.9-1.1.
-
22. The apparatus of claim 21, wherein X is approximately 1.025.
-
23. The apparatus of claim 1, wherein said means for measuring said electrical impedance Z(t) comprises:
-
at least two pairs of electrodes;
a current source generating an alternating current I(t) of predetermined amplitude;
wherein one pair of electrodes is adapted to be connected to said current source;
means for measuring a voltage U(t) caused by applying said alternating current;
wherein one pair of electrodes is connected to said means for measuring the voltage U(t);
means for determining said electrical impedance Z(t) from the voltage U(t) and the current I(t).
-
-
24. The apparatus of claim 1, wherein said means for determining the peak magnitude
-
( Z ( t ) t ) MIN comprises; means for determining Δ
Z(t) from Z(t);
means for calculating
for at least the systolic period of one cardiac cycle;
means for determining the maximum of an input function.
-
-
25. The apparatus of claim 24, wherein said means for determining Δ
- Z(t) is a high-pass filter.
-
26. The apparatus of claim 1, wherein said means for determining Z0 is a low-pass filter.
-
27. The apparatus of claim 1, wherein said means for determining TLVE determines TLVE by determining by analysis of
-
Z ( t ) t a point in time when an aortic valve opens;
a point in time when the aortic valve closes; and
by calculating a time difference of said closing point in time and said opening point in time.
-
-
28. The apparatus of claim 1, wherein said means for determining the cardiac cycle period TRR comprises means for analyzing at least one of a group of Z(t), Δ
- Z(t),
and
- Z(t),
-
29. The apparatus of claim 1, wherein said means for determining the cardiac cycle period TRR comprises means for measuring an electrocardiogram and means for analyzing the measured values.
-
30. The apparatus of claim 1, wherein at least one of said means for determining
-
( Z ( t ) t ) MIN , Z0, TLVE and TRR and said means for calculating are comprised in a processing unit.
-
-
31. The apparatus of claim 1, further comprising means for outputting a signal, which is representative of SV.
-
32. The apparatus of claim 1, further comprising means for visually displaying SV to a user.
-
33. The apparatus of claim 1, further comprising means for calculating an approximate value for a cardiac output CO of the subject'"'"'s heart (in liter/minute), wherein said calculating means is adapted to evaluate a formula
-
1 T RR · 60 1000 .
-
-
34. An apparatus for determining an approximate value for a stroke volume SV of a subject'"'"'s heart, comprising
a) a current source outputting an alternating current I(t) of predetermined amplitude to two electrodes; -
b) means for measuring a voltage U(t) caused by said alternating current between two electrodes; and
c) a processing unit receiving at least a signal representative of U(t), said processing unit being adapted to;
calculate an impedance Z(t) from the voltage U(t) and a value of the current I(t);
input Z(t) into a low-pass filter, an output of said low-pass filter being Z0;
input Z(t) into a high-pass filter, an output of said high-pass filter being Δ
Z(t);
calculate a peak magnitude
ofdetermine a left ventricular ejection time TLVE from at least one of Z(t), Δ
Z(t) and
by using predetermined criteria;
determine a cardiac cycle period TRR of the heart from at least one of Z(t), Δ
Z(t) and
by using predetermined criteria;
calculate SV according to a formula wherein 0.15≦
n≦
0.8 and 0<
m<
1.5,and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant. - View Dependent Claims (35)
-
-
36. An apparatus for determining an approximate value for the stroke volume SV of a subject'"'"'s heart, comprising
a) a current source outputting an alternating current I(t) of predetermined amplitude to two electrodes; -
b) means for measuring a voltage U(t) caused by said alternating current between two electrodes;
c) means for measuring an electrocardiogram; and
d) a processing unit receiving at least a signal representative of U(t) and measured values of said electrocardiogram, said processing unit being adapted to;
calculate an impedance Z(t) from the voltage U(t) and a value of the current I(t);
input Z(t) into a low-pass filter, an output of said low-pass filter being Z0;
input Z(t) into a high-pass filter, an output of said high-pass filter being Δ
Z(t);
calculate a peak magnitude
ofdetermine a left ventricular ejection time TLVE from at least one of Z(t), Δ
Z(t) and
by using predetermined criteria;
determine a cardiac cycle period TRR of the heart from the measured values of said electrocardiogram;
calculate SV according to a formula wherein 0.15<
n<
0.8 and 0<
m<
1.5,and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant. - View Dependent Claims (37)
-
-
38. An apparatus for determining an approximate value for a stroke volume SV of a subject'"'"'s heart, comprising
a) a current source outputting an alternating current I(t) of predetermined amplitude to two electrodes; -
b) means for measuring a voltage U(t) caused by said alternating current between two electrodes;
c) means for measuring an electrocardiogram and means for calculating a cardiac cycle period TRR of the heart from measured values of said electrocardiogram;
d) a processing unit receiving at least a signal representative of U(t) and a signal representative of TRR, said processing unit being adapted to;
calculate an impedance Z(t) from the voltage U(t) and a value of the current I(t);
input Z(t) into a low-pass filter, an output of said low-pass filter being Z0;
input Z(t) into a high-pass filter, an output of said high-pass filter being Δ
Z(t);
calculate a peak magnitude
ofdetermine a left ventricular ejection time TLVE from at least one of Z(t), Δ
Z(t) and
by using predetermined criteria;
calculate SV according to a formula wherein 0.15<
n<
0.8 and 0<
m≦
1.5,and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant. - View Dependent Claims (39, 40)
-
-
41. An apparatus for determining an approximate value for a stroke volume SV of a subject'"'"'s heart, comprising
a) a current source outputting an alternating current I(t) of predetermined amplitude to two electrodes; -
b) means for measuring a voltage U(t) caused by said alternating current between two electrodes;
c) a processor unit receiving at least a signal representative of U(t), said processing unit being adapted to;
calculate an impedance Z(t) from the voltage U(t) and a value of the current I(t);
input Z(t) into a low-pass filter, an output of said low-pass filter being Z0;
input Z(t) into a high-pass filter, an output of said high-pass filter being Δ
Z(t);
calculate a peak magnitude
ofdetermine a left ventricular ejection time TLVE from at least one of Z(t), Δ
Z(t) and
by using predetermined criteria;
calculate SV according to a formula wherein 0.15<
n<
0.8,and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant.
-
-
42. A method of determining an approximate value for a stroke volume SV of a subject'"'"'s heart, comprising the steps of:
-
a) measuring an impedance Z(t) of a part of the subject'"'"'s body, wherein a value of said impedance Z(t) changes with time t as a consequence of the beating of the heart;
b) determining a mean impedance Z0;
c) determining a peak magnitude
of a derivative
of said impedance Z(t) over the time t by using the measured impedance Z(t) for at least a systolic period of one cardiac cycle;
d) determining a left ventricular ejection time, TLVE; and
e) determining a cardiac cycle period TRR of the heart;
f) calculating an approximate value of the stroke volume according to a formula wherein 0.15<
n<
0.8 and 0<
m≦
1.5,and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant. - View Dependent Claims (43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70)
(in milliliter), wherein W is the subject'"'"'s weight in kilogram (kg), wherein C3 is a coefficient with constant value and X and N are exponents with constant values, wherein mZ{overscore (T)}=1 for Z0≧
ZC, and
for Z0<
ZC, and wherein ZC is a constant, and wherein C2 is a constant.
-
-
50. The apparatus of claim 49, wherein C2=0.
-
51. The apparatus of claim 49, wherein C3 is a value in the range of 0.01-15.
-
52. The apparatus of claim 51, wherein C3 is approximately 13.
-
53. The apparatus of claim 49, wherein X is a value in the range of 0.9-1.1.
-
54. The apparatus of claim 53, wherein X is approximately 1.025.
-
55. The apparatus of claim 49, wherein N is a value comprised in the range of 1.0-2.0.
-
56. The apparatus of claim 55, wherein N is approximately 1.5.
-
57. The apparatus of claim 49, wherein ZC is a value in the range of 15-25Ω
- .
-
58. The apparatus of claim 57, wherein ZC is approximately 20Ω
- .
-
59. The apparatus of claim 42, wherein VEFF=C3·
- WX (in milliliter), wherein W is the subject'"'"'s weight in kilogram, and wherein C3 is a coefficient with a constant value and X is an exponent with constant value.
-
60. The apparatus of claim 59, wherein C3 is a value in the range of 0.01-15.
-
61. The apparatus of claim 60, wherein C3 is approximately 13.
-
62. The apparatus of claim 59, wherein X is a value in the range of 0.9-1.1.
-
63. The apparatus of claim 62, wherein X is approximately 1.025.
-
64. The method of claim 42, wherein said impedance Z(t) is measured by applying an alternating current I(t) through the part of the subject'"'"'s body, measuring a voltage drop U(t) in the body caused by the application of said alternating current, and calculating said impedance Z(t) according to a formula
-
( t ) = U ( t ) I ( t ) .
-
-
65. The method of claim 42, wherein said peak magnitude
-
( Z ( t ) t ) MIN is determined by; sending a signal representative of Z(t) through a high-pass filter, an output of said filter being taken to be Δ
Z(t),calculating
for at least the systolic period of one cardiac cycle;
determining an absolute magnitude of said derivative.
-
-
66. The method of claim 42, wherein Z0 is determined by sending a signal representative of Z(t) through a low-pass filter, an output of said filter being Z0.
-
67. The method of claim 42, wherein TLVE is determined by
determining by analysis of -
Z ( t ) t a point in time when an aortic valve opens;
a point in time when the aortic valve closes; and
and by calculating a time difference of said closing point in time and said opening point in time.
-
-
68. The method of claim 42, wherein the cardiac cycle period TRR is determined by analyzing at least one of the group of Z(t), ≢
- Z(t),
and for at least two consecutive cardiac cycles.
- Z(t),
-
69. The method of claim 42, wherein the cardiac cycle period TRR is determined by
measuring an electrocardiogram, and analyzing the measured values. -
70. The method of claim 42, further comprising the step of determining an approximate value for a cardiac output CO of the subject'"'"'s heart, wherein CO (in liter/minute) is determined as the product of SV (in milliliter),
and a constant:
-
71. An apparatus for determining an approximate value for a stroke volume SV (in milliliter) of a subject'"'"'s heart, comprising
a) means for measuring an electrical admittance Y(t) of a part of the subject'"'"'s body, wherein a value of said electrical admittance Y(t) changes with time t as a consequence of the beating of the heart; -
b) means for determining a base admittance Y0 as a part of said electrical admittance Y(t) which does not change significantly during a period of one cardiac cycle;
c) means for determining a peak magnitude
of a temporal derivative
of said electrical admittance Y(t), indicating an absolute maximum rate of change of said electrical admittance Y(t) during a systolic period of the cardiac cycle;
d) means for determining a left ventricular ejection time, TLVE;
e) means for determining the cardiac cycle period TRR of the heart; and
f) means for calculating said approximate value of the stroke volume SV wherein said calculating means is adapted to evaluate a formula wherein 0.15<
n<
0.8 and 0<
m<
1.5,and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant. - View Dependent Claims (72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103)
for Y0>
YC, and wherein YC is a constant, and wherein C2 is a constant.
-
-
79. The apparatus of claim 78, wherein C2=0.
-
80. The apparatus of claim 78, wherein C3 is a value in the range of 0.01-15.
-
81. The apparatus of claim 80, wherein C3 is approximately 13.
-
82. The apparatus of claim 78, wherein X is a value in the range of 0.9-1.1.
-
83. The apparatus of claim 82, wherein X is approximately 1.025.
-
84. The apparatus of claim 78, wherein N is a value in the range of 1.0-2.0.
-
85. The apparatus of claim 84, wherein N is approximately 1.5.
-
86. The apparatus of claim 78, wherein YC is a value in the range of 0.04-0.0667 Ω
-
−
1.
-
−
-
87. The apparatus of claim 86, wherein YC is approximately 0.05 Ω
-
−
1.
-
−
-
88. The apparatus of claim 71, wherein VEFF=C3·
- WX (in milliliter), wherein W is the subject'"'"'s weight in kilogram, and wherein C3 is a coefficient with a constant value and X is an exponent with constant value.
-
89. The apparatus of claim 88, wherein C3 is a value in the range of 0.01-15.
-
90. The apparatus of claim 89, wherein C3 is approximately 13.
-
91. The apparatus of claim 88, wherein X is a value in the range of 0.9-1.1.
-
92. The apparatus of claim 91, wherein X is approximately 1.025.
-
93. The apparatus of claim 71, wherein said means for measuring said electrical admittance Y(t) comprises:
-
at least two pairs of electrodes;
a current source generating an alternating current I(t) of predetermined amplitude;
wherein one pair of electrodes is adapted to be connected to said current source;
means for measuring a voltage U(t) caused by applying said alternating current;
wherein one pair of electrodes is connected to said means for measuring the voltage U(t);
means for determining said electrical admittance Y(t) from the voltage U(t) and the current I(t).
-
-
94. The apparatus of claim 71, wherein said means for determining the peak magnitude
-
Y ( t ) t ) MAX comprises; means for determining Δ
Y(t) from Y(t);
means for calculating
for at least the systolic period of one cardiac cycle;
means for determining the maximum of an input function.
-
-
95. The apparatus of claim 94, wherein said means for determining Δ
- Y(t) is a high-pass filter.
-
96. The apparatus of claim 71, wherein said means for determining Y0 is a low-pass filter.
-
97. The apparatus of claim 71, wherein said means for determining TLVE determines TLVE by determining by analysis of
-
Y ( t ) t a point in time when an aortic valve opens;
a point in time when the aortic valve closes;
and by calculating a time difference of said closing point in time and said opening point in time.
-
-
98. The apparatus of claim 71, wherein said means for determining the cardiac cycle period TRR comprises means for analyzing at least one of a group of Y(t), Δ
- Y(t),
and
- Y(t),
-
99. The apparatus of claim 71, wherein said means for determining the cardiac cycle period TRR comprises means for measuring an electrocardiogram and means for analyzing the measured values.
-
100. The apparatus of claim 71, wherein at least one of said means for determining
-
Y ( t ) t ) MAX , Y0, TLVE and TRR and said means for calculating are comprised in a processing unit.
-
-
101. The apparatus of claim 71, further comprising means for outputting a signal, which is representative of SV.
-
102. The apparatus of claim 71, further comprising means for visually displaying SV to a user.
-
103. The apparatus of claim 71, further comprising means for calculating an approximate value for a cardiac output CO of the subject'"'"'s heart (in liter/minute), wherein said calculating means is adapted to evaluate a formula
-
1 T RR · 60 1000 .
-
-
104. An apparatus for determining an approximate value for a stroke volume SV of a subject'"'"'s heart, comprising
a) a current source outputting an alternating current I(t) of predetermined amplitude to two electrodes; -
b) means for measuring a voltage U(t) caused by said alternating current between two electrodes; and
c) a processing unit receiving at least a signal representative of U(t), said processing unit being adapted to;
calculate an admittance Y(t) from the voltage U(t) and a value of the current I(t);
input Y(t) into a low-pass filter, an output of said low-pass filter being Y0;
input Y(t) into a high-pass filter, an output of said high-pass filter being Δ
Y(t);
calculate a peak magnitude
ofdetermine a left ventricular ejection time TLVE from at least one of Y(t), Δ
Y(t) and
by using predetermined criteria;
determine a cardiac cycle period TRR of the heart from at least one of Y(t), Δ
Y(t) and
by using predetermined criteria;
calculate SV according to a formula wherein 0.15≦
n≦
0.8 and 0<
m≦
1.5,and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant. - View Dependent Claims (105)
-
-
106. An apparatus for determining an approximate value for the stroke volume SV of a subject'"'"'s heart, comprising
a) a current source outputting an alternating current I(t) of predetermined amplitude to two electrodes; -
b) means for measuring a voltage U(t) caused by said alternating current between two electrodes;
c) means for measuring an electrocardiogram; and
d) a processing unit receiving at least a signal representative of U(t) and measured values of said electrocardiogram, said processing unit being adapted to;
calculate an admittance Y(t) from the voltage U(t) and a value of the current I(t);
input Y(t) into a low-pass filter, an output of said low-pass filter being Y0;
input Y(t) into a high-pass filter, an output of said high-pass filter being Δ
Y(t);
calculate a peak magnitude
ofdetermine a left ventricular ejection time TLVE from at least one of Y(t), Δ
Y(t) and
by using predetermined criteria;
determine a cardiac cycle period TRR of the heart from the measured values of said electrocardiogram;
calculate SV according to a formula wherein 0.15<
n<
0.8 and 0<
m≦
1.5,and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant. - View Dependent Claims (107)
-
-
108. An apparatus for determining an approximate value for a stroke volume SV of a subject'"'"'s heart, comprising
a) a current source outputting an alternating current I(t) of predetermined amplitude to two electrodes; -
b) means for measuring a voltage U(t) caused by said alternating current between two electrodes;
c) means for measuring an electrocardiogram and means for calculating a cardiac cycle period TRR of the heart from measured values of said electrocardiogram;
d) a processing unit receiving at least a signal representative of U(t) and a signal representative of TRR, said processing unit being adapted to;
calculate an admittance Y(t) from the voltage U(t) and a value of the current I(t);
input Y(t) into a low-pass filter, an output of said low-pass filter being Y0;
input Y(t) into a high-pass filter, an output of said high-pass filter being Δ
Y(t);
calculate a peak magnitude
ofdetermine a left ventricular ejection time TLVE from at least one of Y(t), Δ
Y(t) and
by using predetermined criteria;
calculate SV according to a formula wherein 0.15<
n<
0.8 and 0<
m≦
1.5,and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant. - View Dependent Claims (109, 110)
-
-
111. An apparatus for determining an approximate value for a stroke volume SV of a subject'"'"'s heart, comprising
a) a current source outputting an alternating current I(t) of predetermined amplitude to two electrodes; -
b) means for measuring a voltage U(t) caused by said alternating current between two electrodes;
c) a processor unit receiving at least a signal representative of U(t), said processing unit being adapted to;
calculate an admittance Y(t) from the voltage U(t) and a value of the current I(t);
input Y(t) into a low-pass filter, an output of said low-pass filter being Y0;
input Y(t) into a high-pass filter, an output of said high-pass filter being Δ
Y(t);
calculate a peak magnitude
ofdetermine a left ventricular ejection time TLVE from at least one of Y(t), Δ
Y(t) and
by using predetermined criteria;
calculate SV according to a formula wherein 0.15<
n<
0.8,and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant.
-
-
112. A method of determining an approximate value for a stroke volume SV of a subject'"'"'s heart, comprising the steps of:
-
a) measuring an admittance Y(t) of a part of the subject'"'"'s body, wherein a value of said admittance Y(t) changes with time t as a consequence of the beating of the heart;
b) determining a mean admittance Y0;
c) determining a peak magnitude
of a derivative
of said admittance Y(t) over the time t by using the measured admittance Y(t) for at least a systolic period of one cardiac cycle;
d) determining a left ventricular ejection time, TLVE; and
e) determining a cardiac cycle period TRR of the heart;
f) calculating an approximate value of the stroke volume according to a formula wherein 0.15<
n<
0.8 and 0<
m≦
1.5,and wherein VEFF is an approximate value of the subject'"'"'s volume of electrically participating tissue, and wherein C1 is a constant. - View Dependent Claims (113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140)
for Y0>
YC, and wherein YC is a constant, and wherein C2 is a constant.
-
-
120. The apparatus of claim 119, wherein C2=0.
-
121. The apparatus of claim 119, wherein C3 is a value in the range of 0.01-15.
-
122. The apparatus of claim 121, wherein C3 is approximately 13.
-
123. The apparatus of claim 119, wherein X is a value in the range of 0.9-1.1.
-
124. The apparatus of claim 123, wherein X is approximately 1.025.
-
125. The apparatus of claim 119, wherein N is a value comprised in the range of 1.0-2.0.
-
126. The apparatus of claim 125, wherein N is approximately 1.5.
-
127. The apparatus of claim 119, wherein YC is a value in the range of 0.04-0.0667 Ω
-
−
1.
-
−
-
128. The apparatus of claim 127, wherein YC is approximately 0.05 Ω
-
−
1.
-
−
-
129. The apparatus of claim 112, wherein VEFF=C3˜
- WX (in milliliter), wherein W is the subject'"'"'s weight in kilogram, and wherein C3 is a coefficient with a constant value and X is an exponent with constant value.
-
130. The apparatus of claim 129, wherein C3 is a value in the range of 0.01-15.
-
131. The apparatus of claim 130, wherein C3 is approximately 13.
-
132. The apparatus of claim 129, wherein X is a value in the range of 0.9-1.1.
-
133. The apparatus of claim 132, wherein X is approximately 1.025.
-
134. The method of claim 112, wherein said admittance Y(t) is measured by applying an alternating current I(t) through the part of the subject'"'"'s body, measuring a voltage drop U(t) in the body caused by the application of said alternating current, and calculating said admittance Y(t) according to a formula
-
( t ) = I ( t ) U ( t ) .
-
-
135. The method of claim 112, wherein said peak magnitude
-
Y ( t ) t ) MAX is determined by; sending a signal representative of Y(t) through a high-pass filter, an output of said filter being taken to be Δ
Y(t),calculating for at least the systolic period of one cardiac cycle; determining an absolute magnitude of said derivative.
-
-
136. The method of claim 112, wherein Y0 is determined by sending a signal representative of Y(t) through a low-pass filter, an output of said filter being Y0.
-
137. The method of claim 112, wherein TLVE is determined by
determining by analysis of -
Y ( t ) t a point in time when an aortic valve opens;
a point in time when the aortic valve closes; and
and by calculating a time difference of said closing point in time and said opening point in time.
-
-
138. The method of claim 112, wherein the cardiac cycle period TRR is determined by analyzing at least one of the group of Y(t), Δ
- Y(t),
and for at least two consecutive cardiac cycles.
- Y(t),
-
139. The method of claim 112, wherein the cardiac cycle period TRR is determined by
measuring an electrocardiogram, and analyzing the measured values. -
140. The method of claim 112, further comprising the step of determining an approximate value for a cardiac output CO of the subject'"'"'s heart, wherein CO (in liter/minute) is determined as the product of SV (in milliliter),
and a constant:
Specification